Re-use assets verbatim if they do not need to change (#448).

7 files changed, 99 insertions, 22 deletions

diff --git a/src/lib/dcp_decoder.cc b/src/lib/dcp_decoder.cc
index 27d0f3a94..59dd7c008 100644
--- a/src/lib/dcp_decoder.cc
+++ b/src/lib/dcp_decoder.cc
@@ -28,6 +28,7 @@
 #include "dcp_decoder.h"
 #include "dcpomatic_log.h"
 #include "digester.h"
+#include "film.h"
 #include "ffmpeg_image_proxy.h"
 #include "frame_interval_checker.h"
 #include "image.h"
@@ -146,6 +147,12 @@ DCPDecoder::DCPDecoder(shared_ptr<const Film> film, shared_ptr<const DCPContent>
 
 	_font_id_allocator.add_fonts_from_reels(_reels);
 	_font_id_allocator.allocate();
+
+	_can_reuse_video = _dcp_content->can_reuse_video(film) && !film->reencode_j2k();
+	_can_reuse_audio = _dcp_content->can_reuse_audio(film);
+	for (int i = 0; i < static_cast<int>(TextType::COUNT); ++i) {
+		_can_reuse_text[i] = _dcp_content->can_reuse_text(film, static_cast<TextType>(i));
+	}
 }
 
 
@@ -176,7 +183,7 @@ DCPDecoder::pass()
 	*/
 	pass_texts(_next, picture_asset->size());
 
-	if ((_j2k_mono_reader || _j2k_stereo_reader || _mpeg2_mono_reader) && (_decode_reusable || !_dcp_content->reference_video())) {
+	if ((_j2k_mono_reader || _j2k_stereo_reader || _mpeg2_mono_reader) && (_decode_reusable || !_can_reuse_video)) {
 		auto const entry_point = (*_reel)->main_picture()->entry_point().get_value_or(0);
 		if (_j2k_mono_reader) {
 			video->emit(
@@ -233,7 +240,7 @@ DCPDecoder::pass()
 		}
 	}
 
-	if (_sound_reader && (_decode_reusable || !_dcp_content->reference_audio())) {
+	if (_sound_reader && (_decode_reusable || !_can_reuse_audio)) {
 		auto const entry_point = (*_reel)->main_sound()->entry_point().get_value_or(0);
 		auto sf = _sound_reader->get_frame(entry_point + frame);
 		auto from = sf->data();
@@ -331,7 +338,7 @@ DCPDecoder::pass_texts(
 	auto const asset = reel_asset->asset();
 	auto const entry_point = reel_asset->entry_point().get_value_or(0);
 
-	if (_decode_reusable || !_dcp_content->reference_text(type)) {
+	if (_decode_reusable || !_can_reuse_text[type]) {
 		auto subs = asset->texts_during(
 			dcp::Time(entry_point + frame, vfr, vfr),
 			dcp::Time(entry_point + frame + 1, vfr, vfr),
@@ -522,10 +529,10 @@ DCPDecoder::set_decode_reusable(bool r)
 	_decode_reusable = r;
 
 	if (video) {
-		video->set_ignore(_dcp_content->reference_video() && !_decode_reusable);
+		video->set_ignore(_can_reuse_video && !_decode_reusable);
 	}
 	if (audio) {
-		audio->set_ignore(_dcp_content->reference_audio() && !_decode_reusable);
+		audio->set_ignore(_can_reuse_audio && !_decode_reusable);
 	}
 }
 
diff --git a/src/lib/dcp_decoder.h b/src/lib/dcp_decoder.h
index dc30526ff..01b85b8d1 100644
--- a/src/lib/dcp_decoder.h
+++ b/src/lib/dcp_decoder.h
@@ -116,4 +116,8 @@ private:
 	std::string _lazy_digest;
 
 	FontIDAllocator _font_id_allocator;
+
+	bool _can_reuse_video;
+	bool _can_reuse_audio;
+	EnumIndexedVector<bool, TextType> _can_reuse_text;
 };
diff --git a/src/lib/player.cc b/src/lib/player.cc
index 86f6e1082..316cf7e2b 100644
--- a/src/lib/player.cc
+++ b/src/lib/player.cc
@@ -758,10 +758,10 @@ Player::pass()
 		earliest_content->done = earliest_content->decoder->pass();
 		auto dcp = dynamic_pointer_cast<DCPContent>(earliest_content->content);
 		if (dcp && !_play_reusable) {
-			if (dcp->reference_video()) {
+			if (dcp->can_reuse_video(film)) {
 				_next_video_time = dcp->end(film);
 			}
-			if (dcp->reference_audio()) {
+			if (dcp->can_reuse_audio(film)) {
 				/* We are skipping some referenced DCP audio content, so we need to update _next_audio_time
 				   to `hide' the fact that no audio was emitted during the referenced DCP (though
 				   we need to behave as though it was).
diff --git a/src/lib/reel_writer.cc b/src/lib/reel_writer.cc
index 67e707d52..2c4fac6e0 100644
--- a/src/lib/reel_writer.cc
+++ b/src/lib/reel_writer.cc
@@ -411,7 +411,7 @@ ReelWriter::finish(boost::filesystem::path output_dcp)
 
 template <class Asset>
 shared_ptr<Asset>
-maybe_reuse_asset(char const* log_name, list<ReusableReelAsset> const& refs, DCPTimePeriod period)
+maybe_reuse_asset(char const* log_name, list<ReusableReelAsset> const& refs, DCPTimePeriod period, boost::filesystem::path output_dir)
 {
 	shared_ptr<Asset> reusable;
 
@@ -423,6 +423,13 @@ maybe_reuse_asset(char const* log_name, list<ReusableReelAsset> const& refs, DCP
 		}
 		if (asset && ref.period == period) {
 			reusable = asset;
+			if (ref.use == ReusableReelAsset::Use::COPY) {
+				auto mxf = reusable->asset_ref().asset();
+				DCPOMATIC_ASSERT(mxf->file());
+				auto const destination = output_dir / mxf->file()->filename();
+				copy_file(*mxf->file(), destination);
+				mxf->set_file(destination);
+			}
 			/* If we have a hash for this asset in the CPL, assume that it is correct */
 			if (reusable->hash()) {
 				reusable->asset_ref()->set_hash(reusable->hash().get());
@@ -484,7 +491,7 @@ ReelWriter::maybe_add_text(
 
 	} else {
 		/* We don't have a subtitle asset of our own; hopefully we have one to reuse */
-		reel_asset = maybe_reuse_asset<dcp::ReelTextAsset>("subtitle", refs, _period);
+		reel_asset = maybe_reuse_asset<dcp::ReelTextAsset>("subtitle", refs, _period, _output_dir);
 	}
 
 	if (reel_asset) {
@@ -519,7 +526,7 @@ ReelWriter::create_reel_picture(shared_ptr<dcp::Reel> reel, list<ReusableReelAss
 		reel_asset = make_shared<dcp::ReelMonoPictureAsset>(_mpeg2_picture_asset, 0);
 	} else {
 		/* We don't have a picture asset of our own; hopefully we have one to reuse */
-		reel_asset = maybe_reuse_asset<dcp::ReelPictureAsset>("picture", refs, _period);
+		reel_asset = maybe_reuse_asset<dcp::ReelPictureAsset>("picture", refs, _period, _output_dir);
 	}
 
 	Frame const period_duration = _period.duration().frames_round(film()->video_frame_rate());
@@ -552,7 +559,7 @@ ReelWriter::create_reel_sound(shared_ptr<dcp::Reel> reel, list<ReusableReelAsset
 		reel_asset = make_shared<dcp::ReelSoundAsset>(_sound_asset, 0);
 	} else {
 		/* We don't have a sound asset of our own; hopefully we have one to reuse */
-		reel_asset = maybe_reuse_asset<dcp::ReelSoundAsset>("sound", refs, _period);
+		reel_asset = maybe_reuse_asset<dcp::ReelSoundAsset>("sound", refs, _period, _output_dir);
 	}
 
 	auto const period_duration = _period.duration().frames_round(film()->video_frame_rate());
diff --git a/src/lib/reusable_reel_asset.cc b/src/lib/reusable_reel_asset.cc
index ab14460e0..3894cc4e0 100644
--- a/src/lib/reusable_reel_asset.cc
+++ b/src/lib/reusable_reel_asset.cc
@@ -50,8 +50,12 @@ maybe_add_asset(list<ReusableReelAsset>& a, shared_ptr<dcp::ReelFileAsset> r, Fr
 	r->set_duration (r->actual_duration() - reel_trim_start - reel_trim_end);
 	if (r->actual_duration() > 0) {
 		a.push_back (
-			ReusableReelAsset(r, DCPTimePeriod(from, from + DCPTime::from_frames(r->actual_duration(), ffr)), ReusableReelAsset::Use::REFERENCE)
-			);
+			ReusableReelAsset(
+				r,
+				DCPTimePeriod(from, from + DCPTime::from_frames(r->actual_duration(), ffr)),
+				reference ? ReusableReelAsset::Use::REFERENCE : ReusableReelAsset::Use::COPY
+			)
+		);
 	}
 }
 
@@ -69,7 +73,12 @@ get_reusable_reel_assets(shared_ptr<const Film> film, shared_ptr<const Playlist>
 			continue;
 		}
 
-		if (!dcp->reference_video() && !dcp->reference_audio() && !dcp->reference_text(TextType::OPEN_SUBTITLE) && !dcp->reference_text(TextType::CLOSED_CAPTION)) {
+		if (
+			!dcp->can_reuse_video(film) &&
+			!dcp->can_reuse_audio(film) &&
+			!dcp->can_reuse_text(film, TextType::OPEN_SUBTITLE) &&
+			!dcp->can_reuse_text(film, TextType::CLOSED_CAPTION)
+		   ) {
 			continue;
 		}
 
@@ -107,21 +116,21 @@ get_reusable_reel_assets(shared_ptr<const Film> film, shared_ptr<const Playlist>
 			Frame const reel_trim_end =   min(reel_duration, max(int64_t(0), reel_duration - (offset_from_end - trim_end)));
 
 			auto const from = content->position() + std::max(DCPTime(), DCPTime::from_frames(offset_from_start - trim_start, frame_rate));
-			if (dcp->reference_video()) {
-				maybe_add_asset (reel_assets, reel->main_picture(), reel_trim_start, reel_trim_end, from, frame_rate);
+			if (dcp->can_reuse_video(film)) {
+				maybe_add_asset(reel_assets, reel->main_picture(), reel_trim_start, reel_trim_end, from, frame_rate, dcp->reference_video());
 			}
 
-			if (dcp->reference_audio()) {
-				maybe_add_asset (reel_assets, reel->main_sound(), reel_trim_start, reel_trim_end, from, frame_rate);
+			if (dcp->can_reuse_audio(film)) {
+				maybe_add_asset(reel_assets, reel->main_sound(), reel_trim_start, reel_trim_end, from, frame_rate, dcp->reference_audio());
 			}
 
-			if (dcp->reference_text(TextType::OPEN_SUBTITLE) && reel->main_subtitle()) {
-				maybe_add_asset (reel_assets, reel->main_subtitle(), reel_trim_start, reel_trim_end, from, frame_rate);
+			if (dcp->can_reuse_text(film, TextType::OPEN_SUBTITLE) && reel->main_subtitle()) {
+				maybe_add_asset(reel_assets, reel->main_subtitle(), reel_trim_start, reel_trim_end, from, frame_rate, dcp->reference_text(TextType::OPEN_SUBTITLE));
 			}
 
-			if (dcp->reference_text(TextType::CLOSED_CAPTION)) {
+			if (dcp->can_reuse_text(film, TextType::CLOSED_CAPTION)) {
 				for (auto caption: reel->closed_captions()) {
-					maybe_add_asset (reel_assets, caption, reel_trim_start, reel_trim_end, from, frame_rate);
+					maybe_add_asset(reel_assets, caption, reel_trim_start, reel_trim_end, from, frame_rate, dcp->reference_text(TextType::CLOSED_CAPTION));
 				}
 			}
 
diff --git a/test/reuse_test.cc b/test/reuse_test.cc
new file mode 100644
index 000000000..54d98abe9
--- /dev/null
+++ b/test/reuse_test.cc
@@ -0,0 +1,49 @@
+/*
+    Copyright (C) 2026 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+#include "lib/dcp_content.h"
+#include "lib/film.h"
+#include "lib/ratio.h"
+#include "test.h"
+#include <boost/test/unit_test.hpp>
+
+
+using std::make_shared;
+
+
+BOOST_AUTO_TEST_CASE(reuse_whole_dcp_test)
+{
+	boost::filesystem::path const source = "test/data/scaling_test_133_185";
+	auto dcp = make_shared<DCPContent>(source);
+	auto film = new_test_film("reuse_basic_test", { dcp });
+	film->set_container(Ratio::from_id("185"));
+	film->set_audio_channels(8);
+	make_and_verify_dcp(
+		film,
+		{
+			dcp::VerificationNote::Code::INVALID_STANDARD,
+		});
+
+	auto const output = film->dir(film->dcp_name());
+	check_file(source / "j2c_97b50c93-ad3a-45d7-8ce0-4b875302a704.mxf", output / "j2c_97b50c93-ad3a-45d7-8ce0-4b875302a704.mxf");
+	check_file(source / "pcm_156782ba-4cae-4468-b3ea-1126be23b6d6.mxf", output / "pcm_156782ba-4cae-4468-b3ea-1126be23b6d6.mxf");
+}
+
diff --git a/test/wscript b/test/wscript
index a4a96c381..d16717704 100644
--- a/test/wscript
+++ b/test/wscript
@@ -158,6 +158,7 @@ def build(bld):
                  remake_video_test.cc
                  remake_with_subtitle_test.cc
                  render_subtitles_test.cc
+                 reuse_test.cc
                  scaling_test.cc
                  scoped_temporary_test.cc
                  silence_padding_test.cc